A systematic review of methodology applied during preclinical anesthetic neurotoxicity studies: important issues and lessons relevant to the design of future clinical research

Abstract

Preclinical evidence suggests that anesthetic agents harm the developing brain thereby causing long-term neurocognitive impairments. It is not clear if these findings apply to humans, and retrospective epidemiological studiesthus far have failed to show definitive evidence that anesthetic agents are harmful to the developing human brain.

AIM:

The aim of this systematicreview was to summarize the preclinicalstudies published over the past decade, with a focus on methodological issues, to facilitate the comparison between different preclinicalstudies and inform better design of future trials.

METHOD:

The literature search identified 941 articles related to the topic of neurotoxicity. As the primary aim of thissystematicreview was to compare methodologies applied in animal studies to inform future trials, we excluded a priori all articles focused on putative mechanism of neurotoxicity and the neuroprotective agents. Forty-seven preclinicalstudies were finally included in this review.

RESULTS:

Methods used in these studies were highly heterogeneous-animals were exposed to anesthetic agents at different developmental stages, in various doses and in various combinations with other drugs, and overall showed diverse toxicity profiles. Physiological monitoring and maintenance of physiological homeostasis was variable and the use of cognitive tests was generally limited to assessment of specific brain areas, with restricted translational relevance to humans.

CONCLUSION:

Comparison between studies is thus complicated by this heterogeneous methodology and the relevance of the combined body of literature to humans remains uncertain. Future preclinicalstudies should use better standardized methodologies to facilitate transferability of findings from preclinical into clinical science.